Optical system for semiconductor lithography

ABSTRACT

An optical system for semiconductor lithography including a plurality of optical components, as well as related components and methods, are disclosed. The apparatus can include an optical component that can be moved by a distance along a straight line within a time of between 5 ms and 500 ms. The straight line can have a polar and azimuth angle of between 0° and 90°, and a distance between the straight line and an optical axis of the apparatus being less than a cross-sectional dimension of a projection exposure beam bundle of the projection exposure apparatus. The apparatus can also include a guide unit configured to guide the optical component. The apparatus can further include a drive unit configured to drive the optical component via drive forces so that torques generated by inertial forces of the optical component and of optional components concomitantly moved with the optical component, and the torques generated by the drive forces, which act on the guide unit, compensate for one another to less than 10%.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims benefit under 35 USC120 to, U.S. application Ser. No. 12/372,095, filed Feb. 17, 2009, nowU.S. Pat. No. 8,269,947, which is a continuation of, and claims priorityunder 35 USC 120 to, international application PCT/EP2007/007256, filedAug. 16, 2007, which claims benefit of U.S. Ser. No. 60/822,547, filedAug. 16, 2006 and German Application No. 10 2006 038 455.5, filed Aug.16, 2006. U.S. application Ser. No. 12/372,095 and internationalapplication PCT/EP2007/007256 are hereby incorporated by reference intheir entirety.

FIELD

The disclosure relates to an optical system for semiconductorlithography including a plurality of optical components, as well asrelated components and methods.

BACKGROUND

Optical systems for semiconductor lithography can be flexibly set to awide variety of operational configurations.

SUMMARY

In some embodiments, the disclosure provides a device and a method whichpermit the rapid changing of the operational configuration of an opticalsystem for semiconductor lithography.

In one aspect, the disclosure provides an optical system configured tobe used in semiconductor microlithography. The optical system includes aplurality of optical components and an actuating unit. The actuatingunit is configured to position at least one of the plurality of opticalcomponents at defined positions along an optical axis of the opticalsystem to set different operational configurations of the opticalsystem. The actuating unit acts on the optical component at at least onepoint of action, and the actuating unit is configured so that it ispossible to change between two different operational configurationswithin a time period of less than 500 ms.

In another aspect, the disclosure provides a method that includeschanging between two different operational configurations of an opticalsystem for semiconductor lithography in a time period of less than 50 msby positioning at least one optical component of a plurality of opticalcomponents of the optical system along an axis of the optical system.

In a further aspect, the disclosure provides an illumination system fora projection exposure apparatus in semiconductor lithography. Theillumination system includes an optical element configured to set alight distribution in a pupil plane of the system. The illuminationsystem also includes a manipulable optical component arranged in a lightpath upstream of the optical element so that different regions of theoptical element can be illuminated by manipulating the opticalcomponent.

In an additional aspect, the disclosure provides a lithographicprojection exposure apparatus. The apparatus includes an opticalcomponent that can be moved by a distance along a straight line. Thestraight line has a polar and azimuth angle of between 0° and 90°. Adistance between the straight line and an optical axis of the apparatusbeing less than a cross-sectional dimension of a projection exposurebeam bundle of the projection exposure apparatus. The apparatus alsoincludes a guide unit configured to guide the optical component. Theapparatus further includes a drive unit configured to drive the opticalcomponent via drive forces so that torques generated by inertial forcesof the optical component and of optional components concomitantly movedwith the optical component, and the torques generated by the driveforces, which act on the guide unit, compensate for one another down toa magnitude of less than 10%.

In another aspect, the disclosure provides an illumination system for aprojection exposure apparatus in semiconductor lithography. Theillumination system includes an optical component configured to set aradiation distribution in a pupil plane of the system, the opticalcomponent comprising at least two optical partial elements. Each of thepartial optical components is capable of being introduced periodicallyat a frequency into a beam bundle used to illuminate. The illuminationsystem also includes a source of pulsed electromagnetic radiationconfigured to generate the beam bundle, a pulse frequency of theelectromagnetic radiation corresponding to the frequency at which thepartial elements are introduced into the beam bundle.

In some embodiments, the optical system for semiconductor lithographyincludes a plurality of optical components, where, for setting differentoperational configurations of the optical system, there is at least oneactuating unit for positioning at least one optical component at definedpositions along an optical axis of the optical system. In this case, theactuating unit acts on the optical component at at least one point ofaction and is designed so that it is possible to change between twodifferent operational configurations within a time period of less than500 ms (e.g., 50 ms). Appropriate optical components include all opticalelements that are usually used in optical systems, such as, for example,lenses, mirrors, diaphragms, plane-parallel plates or else diffractiveoptical elements such as, for example, diffraction gratings, in eachcase with mounts, if appropriate.

The optical system can be, for example, an illumination system or else aprojection objective of a lithographic projection exposure apparatus.

In some embodiments, the points of action of the actuating unit on theoptical component are chosen in such a way that no moments arise on theoptical component. In other words, as a result of the acceleration ofthe optical components during their movement for positioning, no torquesor tilting moments take effect on the optical component. This means thatonly a linear acceleration is present at the optical component as aresult. As soon as the optical component has reached the desiredposition, only the inertial forces resulting from the linearacceleration have to be compensated for in order to prevent oreffectively attenuate a subsequent oscillation of the optical component.In this case, a linear acceleration encompasses positive accelerations,during which the kinetic energy of the optical component increases withrespect to time, and also negative accelerations or decelerations, inwhich the kinetic energy of the optical component decreases with respectto time. By way of example, the linear acceleration of the opticalcomponent is provided shortly before reaching a desired end position viaa retardation of the optical component. In this case, the forces of theactuating unit act on the optical component in such a way according tothe disclosure that after vector addition of all the forces (includingthe inertial forces), no resultant torque having a componentperpendicular to the acceleration takes effect on the optical component.Optionally, the resultant torque is zero, or less than 10% with regardto its magnitude, such as less than 1% of the magnitude of the maximumoccurring individual torque generated by the forces (including inertialforces). In this case, the lower limit for the resultant torque alsodepends, inter alia, on the friction occurring in the actuating unit. Asa result, this has the effect that the time required overall forpositioning the optical component is significantly reduced by comparisonwith certain known times. This is because avoiding the resultant torquementioned considerably reduces or completely prevents the oscillationexcitation of the actuating unit and/or of a guide unit for the opticalcomponent (for the precise linear guidance thereof), by the movement ofthe optical component, such that possible oscillation amplitudes of theoptical element do not affect the desired end position of the element.This affords the possibility of switching an optical system forsemiconductor lithography from one operational configuration to anotherwithin extremely short time periods.

The optical component's freedom from moments during the adjustingprocess as outlined above can be achieved in this case by virtue of thefact that precisely one point of action of the actuating unit on theoptical component is present, which is chosen in such a way that thevector of the force exerted on the optical component by the actuatingunit at the point of action runs through the centroid of the opticalcomponent. By virtue of the fact that the actuating unit acts on theoptical component only at one location and the vector of the forceexerted on the optical component by the actuating unit runs through thecentroid of the optical component, the required freedom from moments orthe moment equilibrium can be ensured in a simple manner. This variantneed not involve the force that is exerted on the optical component atdifferent points by one or a plurality of actuating units to beapportioned in such a way that a moment equilibrium or a freedom frommoments for the optical component arises as a result—this requirement isautomatically fulfilled by the choice of the point of action and thedirection of the force.

As a result of geometrical conditions of the device it may beappropriate to provide precisely two points of action of the actuatingunit on the optical component. In this case, the desired mechanicalbehavior of the optical component can be achieved by virtue of the factthat the points of action are chosen in such a way that the centroid ofthe optical component lies on the area which is defined by a straightline through the two points of action and the vector of the resultantforce acting on the optical component. In this case, the opticalcomponent can be moved at the points of action either by one actuatingunit or by two actuating units for positioning. In this case, the use ofjust one actuating unit for positioning has the advantage that acoordination of the forces acting on the optical component at the pointsof action is already inherently ensured by this structural measure.Since only one actuating unit acts on the optical component, it isensured that the forces acting at the two points of action are always inthe same relationship with respect to one another, which is determinedonly by the geometry of the arrangement and not by the forces exerted bydifferent actuating units. It goes without saying that the actuatingunit can also act on the optical component via more than two points ofaction; in this case, it is merely necessary to ensure that no resultanttorques or tilting moments arise at the optical component as a result.

In this case, it has proved worthwhile to embody the actuating unit insuch a way that it has at least one Lorentz linear actuator. In thiscase, a Lorentz linear actuator is understood to be a linear motor inwhich a translational, linear movement is achieved directly on accountof the force interaction between magnets that is based on the Lorentzforce. In this case, the magnets can be realized as coils through whichcurrent flows, that is to say as electromagnets, or—in some instances—aspermanent magnets. One advantage of using Lorentz linear actuators isthat extremely rapid movements can be realized in a precise manner usingthe actuators. In this case, the Lorentz linear actuator operatespractically contactlessly and hence in a manner free of wear andmaintenance; furthermore, the force exerted by the Lorentz linearactuator is dependent only on the current flowing through the coils andnot on the present actuator position. As a result, the use of the linearactuator permits the positioning of an optical component over travels ofa few cm, such as in the region of 20 cm, with an accuracy in the μmrange within a time period of less than 500 ms, such as less than 50 ms.

For the case where the Lorentz linear actuator has permanent magnets, itis advantageous if the magnets are mechanically connected to the opticalcomponent. The arrangement of the permanent magnets on the opticalcomponent has the advantage that the desire for a cabling of the opticalcomponent to be moved, as would be necessary in the case of using coilsthrough which current flows, is effectively avoided in this way and themobility of the optical component is therefore not restricted by thecabling as a result. This variant is advantageous particularly for thosecases where the optical component is intended to be positioned over alonger path, in particular in the region of greater than 50 mm.

For cases where the optical component is positioned over a shorter path,it can also be advantageous if the Lorentz linear actuator has coilsthat are mechanically connected to the optical component. Although thisprocedure has the implication that the electrical cables required formaking contact with the coils have to be concomitantly moved, thisprocedure has the advantage that the coils used usually have a smallerweight than the permanent magnets, such that the inertial forcesresulting from the accelerations of the optical component are lower thanin the case of using permanent magnets.

The technical characteristics of the Lorentz linear actuator as outlinedabove make it possible for at least one Lorentz linear actuator to bedesigned to position a plurality of optical components. Via suitabledriving of the coils through which current flows, it is possible in thiscase to achieve a mutually independent movement of different opticalcomponents via the same Lorentz linear actuator. The apparatus outlayand hence the complexity of the overall system can be effectivelylimited in this way.

For guiding the movement of the optical component during thepositioning, a linear guide has proved to be worthwhile, which guide canbe a rolling bearing guide or as an aerostatic bearing, such as a gasbearing, air bearing or air cushion bearing. In this case, the linearguide ensures that the optical element, during its positioning, does notexperience an offset or tilting with respect to the optical axis of theoptical system. The use of a linear guide with rolling bearings—as ballrecirculation or cross roller guide—has the advantage that a guide ofthis type can be realized in very stiff fashion.

The functioning of an aerostatic bearing is based on the fact that twoelements moved relative to one another are separated by a thin gas filmand therefore do not come into mechanical contact with one another. Inthis way, the elements are enabled to be moved relative to one anotherin a manner exhibiting very little wear and friction, whereby particleabrasion that leads to contaminations can also be avoided. In this case,the gas film can be established dynamically by feeding in gas. The purgegas—generally nitrogen—used anyway in optical systems for semiconductorlithography can advantageously be employed as the gas.

An encoder having a measuring head and a reference grating can be usedfor determining the position of the optical component. In this case, thereference grating can be realized as a line grating structure on aplastic film adhesively bonded onto the optical component. The measuringhead registers the number of lines passing it during a movement of theoptical component and derives the position of the optical componenttherefrom. It goes without saying that it is also conceivable for themeasuring head to be arranged on the optical component; this isadvantageous primarily when the structural space is greatly restrictedin an axial direction.

A compensation device can be employed for the compensation of the weightforce acting on the optical component, the compensation device beingrealized for example as a counterweight or as a frictionless pneumaticcylinder with gap seals. This variant has the advantage that it ispossible to avoid contamination of the interior of the optical system byescaping gas. The compensation of the weight force has the effect thatin the rest state the optical component does not have to be held by theactuating unit against the weight force and heating of the actuatingunit in the rest state is thus prevented.

The actuating unit can be designed so that it includes an axialactuating mechanism for positioning the optical component in a directionof an optical axis of the optical system and a pivoting mechanism forpivoting the optical component out of or into the beam path of theoptical system. It goes without saying that it is also conceivable foronly the pivoting mechanism to be connected, and for a movement of theoptical component in an axial direction not to be provided. This measurehas the effect that optical components, as long as they are situatedoutside the beam path of the optical system, can be brought ready to theaxial position at which they are intended to be situated in a newoperational configuration of the optical system. In this case, the axialpositioning of the optical components can already be effected during theoperation of the optical system in the old operational configuration;for setting the new operational configuration it then suffices merely topivot the relevant optical components into the beam path of the opticalsystem, thus reducing the time required for changing from oneoperational configuration to the next. For this purpose, it isadvantageous if the pivoting mechanism and the axial actuating mechanismare designed so that there is a free travel of the optical component inan axial direction if the optical component is pivoted out of the beampath of the optical system.

Since a comparatively long time, usually between one and six seconds, isavailable on account of the variant outlined above for the axialpositioning of the optical components, the requirements made of theaxial actuating mechanism are comparatively moderate. They can bespindle drives, Lorentz linear actuators, toothed racks or else cablepulls.

In this case, the pivoting mechanism can a rotatable element; thecentroid of the arrangement of pivoting mechanism and optical componentcan advantageously be arranged in the region of the axis of rotation ofthe pivoting mechanism; rotational oscillations of the optical componentcan be avoided particularly effectively in this way. If the centroid ison the axis of rotation, then the sum of the centrifugal or centripetalforces is advantageously zero. As a result, the axis of rotation is notburdened by a possible unbalance. An oscillation excitation of the axisof rotation and thus also an oscillation excitation of the opticalelement or of the optical component are thus effectively avoided,whereby a precise positioning of the optical component within a veryshort time becomes possible. Furthermore, it is advantageous to designthe pivoting mechanism in stiff and lightweight fashion for avoidingoscillations. Materials having a large modulus of elasticity with lowdensity, that is to say for example titanium alloys or else carbon fibercomposite materials, are appropriate for realizing the pivotingmechanism. Because only individual optical components are pivoted intothe beam path of the optical system, the accelerated masses and hencethe resultant inertial forces are small—also on account of theaforementioned choice of the materials for the pivoting mechanism—, suchthat fast movements can be realized without excessively severeoscillations of the device occurring. In this case, the pivotingoperation mentioned is effected within 500 ms, such as within 50 ms, inmodern lithography apparatuses within 10 ms. It should be mentioned thatit is also possible for more than one optical component to be pivotedinto the beam path, or with the pivoting of an optical component or agroup of optical components into the beam path of a lithographicprojection exposure apparatus it is possible at the same time for atleast one other optical component to be pivoted out of the beam path.Thus, e.g. just by pivoting optical components into and out of the beampath of a projection exposure apparatus for example in a zoom axiconsystem, it is possible to obtain two different configurations withregard to the illumination setting respectively arising.

For rapidly pivoting the optical components into the beam path it hasproved worthwhile to embody the pivoting mechanism in such a way thatthey have a prestress element and a releasable retention element. It isthus possible to establish a prestress relative to the retention elementeven before the optical component is pivoted into the beam path; afterthe release of the retention element, the full force is then immediatelypresent at the optical component, which can then be introduced rapidlyinto the beam path. In this case, the prestress element can be realizedas an electromagnet, for example.

As a further variant of the arrangement according to the disclosure, atleast two actuating units having in each case at least one axialactuating mechanism and in each case at least one pivoting mechanismassigned to the axial actuating mechanism can be present. In this case,the optical components that can be positioned by the actuating units canbe substantially identical or else different with regard to theiroptical properties. The coupling of the optical component(s) to theactuating units can be effected in such a way that, as illustratedabove, the oscillation excitation of actuating units and/or guide unitsfor guiding the optical component, such as e.g. the axis of rotation,are minimal.

In a further advantageous variant of the disclosure, at least one of theoptical components has a centering tolerance within the range of between30 μm and 60 μm. The centering tolerance of the relevant opticalcomponent to be positioned is thus higher than the centering toleranceof the optical components fixedly incorporated in the optical system.The higher centering tolerance of the optical components to bepositioned can be achieved for example by a corresponding rebudgeting inthe design of the optical system. As a result of the higher centeringtolerance of the optical components to be positioned, the requirementsmade of the actuating unit and the mechanisms assigned thereto decrease,thus reducing the outlay in the construction and realization of thedevice according to the disclosure.

As a further possibility, e.g. for the case where the optical componentis mounted such that it is pivotable or rotatable with respect to abearing point, the optical component can be mechanically connected to abalancing mass in order to reduce parasitic forces/moments. In thiscase, the balancing mass can have a larger mass than the mass of theoptical component, which can be compensated for by virtue of the factthat the distance between the centroid of the balancing mass and thebearing point is less than the distance r between the centroid of theoptical component and the bearing point. The balancing mass can itselfagain be formed by an optical component.

The disclosure described above can advantageously be used in anillumination system for a projection exposure apparatus in semiconductorlithography. In this case, the illumination system can include anoptical element, e.g. a micromirror array, which can serve for setting alight distribution in a pupil plane of the illumination system. Forsetting or for supporting the setting of the light distribution, amanipulable optical component is arranged in the light path upstream ofthe optical element in such a way that different regions of the opticalelement, such as e.g. of the micromirror array, can be illuminated by amanipulation of the optical component.

The manipulable optical component can be a mirror which is movable, suchas displaceable or tiltable, in the light path. It is likewise possibleto use a diffractive optical element which can be introduced, such asinserted, into the light path, a conical lens of an axicon or arefractive optical component.

In addition, it is advantageous if optically active elements forpolarization rotation are arranged in the light path upstream of theoptical element, which elements can be used to set differentpolarizations for the different regions of the optical element; thearrangement of at least one neutral filter in the light path upstream ofthe optical element is also conceivable.

Some exemplary embodiments of the disclosure are explained in moredetail below with reference to the drawings.

In the figures:

FIG. 1 shows a device according to the disclosure;

FIG. 2 shows a first variant of the present disclosure;

FIG. 2a shows a schematic bearing device for moving an optical elementaccording to the prior art;

FIG. 2b shows a bearing device according to FIG. 2a with an end positionof the optical component and possible oscillations thereof;

FIG. 2c shows a schematic illustration of a further variant of thepresent disclosure, with a guide device for guiding the opticalcomponent and an actuating unit or drive device, for linearly displacingthe optical component;

FIG. 2d shows an embodiment according to FIG. 2c taking account offriction in the guide device;

FIG. 2e shows a schematic illustration of the forces that occur in anembodiment according to FIG. 2c taking account of the friction accordingto FIG. 2 d;

FIG. 2f shows a further embodiment of the disclosure with drive forcesacting on the edge of the optical component;

FIG. 2g shows a further embodiment of the disclosure;

FIGS. 3a-3c show various possibilities for varying the arrangement ofoptical component, actuating units and linear guide;

FIG. 4 shows a variant of the disclosure in which the linear guides arerealized as air bearings;

FIGS. 5a-5b show two embodiments of the device according to thedisclosure in which the weight force of the optical component iscompensated for;

FIG. 6 shows a further embodiment of the device according to thedisclosure, in which the optical components, in addition to adisplacement in a direction of the optical axis of the optical system,can also be pivoted out of the region of the optical axis or into theregion of the optical axis;

FIG. 7 shows an embodiment of a pivoting mechanism for pivoting theoptical component into and out of the beam path of the optical system;

FIG. 8 shows an example of the use of a balancing mass;

FIG. 9 shows a part of an illumination system of a projection exposureapparatus for semiconductor lithography;

FIG. 10 shows partial regions of a micromirror array and correspondinglight distributions in a pupil plane;

FIGS. 11a-11b show a first possibility for setting a light distributionon a micromirror array;

FIG. 12 shows a further possibility for setting a light distribution ona micromirror array;

FIG. 13 shows a possibility for selectively choosing the polarization indifferent regions of the pupil plane;

FIG. 14 shows an additional possibility for setting a light distributionon a micromirror array using a so-called axicon;

FIG. 15 shows a neutral filter for use in an optical system according tothe disclosure; and

FIG. 16 shows a further possibility for setting a light distributionwithout linearly accelerated elements.

FIG. 1 shows a device according to the disclosure. In this case, theoptical component 1 is moved via the actuating units 2 along the opticalaxis, which in the present case runs perpendicular to the plane of thedrawing. In the present case, the two actuating units 2 are realized asLorentz linear actuators with permanent magnets 4 and coils 5; in thiscase, the permanent magnets 4 are mechanically connected to the opticalcomponent 1 via a respective point of action 3. As indicated in FIG. 1,in this case the straight line through the two points of action 3 runsthrough the centroid—designated by “S”—of the optical component 1. Thisarrangement of the points of action has the advantage that, assuming anat least approximately identical behavior of the actuating units 2, theoptical component 1 can be moved without torques acting on it. What isachieved in this way is that oscillations of the optical component 1during or after the positioning, which oscillations could originate fromsuch torques, cannot arise. As a result this provides a possibility ofmoving the optical component 1 very rapidly along the optical axis tothe desired position in the optical system, since, firstly, the timeperiod required for the optical component 1 to come to rest afterreaching its position in the optical system is significantly shortenedand, secondly, overall higher speeds become possible for the positioningof the optical component 1. In this case, the movement of the opticalcomponent 1 along the optical axis is stabilized by the linear guide 6and measured by the displacement measuring system 12. The displacementmeasuring system 12 can be a so-called encoder whose measuring head 15is fixedly connected to the housing (not illustrated in FIG. 1) of theoptical system and whose reference grating 16 is concomitantly movedwith the optical component 1; it is likewise conceivable to arrange themeasuring head 15 on the optical component 1 and to fixedly connect thereference grating 16 to the housing of the optical system. The secondvariant is advantageous particularly when little structural space isavailable in an axial direction. Instead of an encoder measuring system,it is alternatively possible to use a different position detectingsystem if the latter has the required accuracy. A position detectingsystem is ideally used for each Lorentz linear actuator.

FIG. 2 shows a variant which differs from FIG. 1 in terms of theconcrete configuration of the actuating unit 2. In the variant shown inFIG. 2, in contrast to FIG. 1, the coils 5 rather than the permanentmagnets 4 are mechanically connected to the optical component 1, that isto say that the coils 5 concomitantly move with the optical component 1.What is advantageous about this variant is that the coils 5 generallyhave a smaller mass than the permanent magnets 4, whereby the mass movedin total is reduced. This variant can be expedient for the realizationof short adjusting distances, where making electrical contact with thecoils 5 via cable connections, for example, is unproblematic.

In order to illustrate the advantages of the present disclosure, atechnical embodiment of an adjustable optical component 1 with anadjusting unit known in the prior art is described schematicallyreferring to FIG. 2a . In this case, the optical component 1 isdisplaced along an optical axis 200. In order to produce this lineardisplacement of the optical component 1, an actuating unit is used whichmoves a slide 62 by a magnitude X along the coordinate axis X, and inthis case the optical component 1 moves by substantially the samemagnitude X along the optical axis 200. As shown in FIG. 2a , the slide62 can be guided via a guide 63, wherein the guide axis 60 issubstantially parallel to optical axis 200 within mechanical productionand alignment tolerances.

The optical component 1 illustrated in FIG. 2a is connected to the slide62 via a connection 64 (not illustrated in more specific detail). Theoptical component 1 is a refractive element, for example, which caninclude polyhedral and/or convex or concave surfaces 101, 102. The guide63 and the slide 62 usually form a driven actuating unit such as can berealized e.g. via the linear actuators described above. In this case,e.g. the slide 62 is moved along the guide 63 via electromagneticforces. A force F is required for accelerating the slide 62 and theoptical component 1, and also for overcoming the friction force of theactuating unit. If the friction force is initially disregarded, then anacceleration a=F/(m+ms) results from the force F taking account of themass m of the optical component 1. In this case, the mass of the slide62 is designated by ms. This acceleration brings about an inertial forceF_(T), which acts on the centroid 103 of the optical component 1 andwhich results as F_(T)=m*a. If the optical component 1 is constructed insuch a way that its centroid is displaced along the optical axis 200,then F_(T) acts along the optical axis 200. It should be mentioned,however, that for the present exemplary embodiment and for thesubsequent exemplary embodiments it is not necessarily a requirementthat the centroid of the optical component or the centroid of the systemof optical components 1 and slide 62 moves along the optical axis 200.The centroids can alternatively also move along an axis displacedparallel to the optical axis 200.

Disregarding possible bearing play of the slide 62 perpendicular to theguide axis 60 of the actuating unit including the guide 63 and the slide62, and likewise disregarding the geometrical extent of the guide 63 inthis direction, e.g. since the distance b between the optical axis 200and the guide axis 60 is very much greater than the extent of the guide63, the inertial force F_(T) generates a torque M_(T)=b*F_(T) orientedin a direction perpendicular to the guide axis 60. A further torque inthis direction can be generated e.g. by the inertial force of the slide62 if its centroid does not lie on the guide axis 60 of the guide 63.

The torques generated by the inertial forces dynamically load the guide63 and the slide 62 (and the optical component 1), such that theseelements are excited to effect constrained oscillations as a result ofthe torque input, or as a result of the forces caused by the torques. Ifthe optical component 1 is transferred from a position A (see FIG. 2a )into an end position B (see FIG. 2b ), the deceleration of the opticalcomponent 1 on account of its inertial force F_(T) brings about a torqueM_(T) which brings about excitation to form oscillations mentionedabove. The excitation of such oscillations can result in an oscillation202 of the optical component 1, wherein an imaginary plane 201 throughthe optical component 1, running perpendicular to the optical axis 200,oscillates about an axis C. The position of this oscillation axis C neednot coincide with the position and direction of the torque M_(T) asshown in FIG. 2b . Rather, the position and the direction of this axisof rotation C depend on the constrained oscillations, wherein theposition of the axis of rotation C is substantially determined by thegeometry of the guide 63 and of the slide 62 since the effect of thetorque M_(T) is substantially taken up by this guide device 62, 63. InFIGS. 2a and 2b , tilting oscillations are also produced by the torqueM_(T). The tilting oscillations are not damped by the drive device,which can be, for example, a Lorentz linear drive, rather they arepredominantly damped by the damping effect of the guide device 62, 63.This damping effect is very small, however, particularly in the case of“frictionless” bearing, which is why, according to the inventors'knowledge, a tilting oscillation excitation by the torque makes a fastprecision positioning very difficult or even impossible, as is alsoexplained in more detail below.

In order to position the optical component 1 within less than 500 msdown to less than 50 ms, in modern lithography apparatuses even within 5ms, to approximately 10 μm down to 1 μm accuracy with respect to the endpoint B of its displacement, it is necessary for the optical component 1to reach its end position with as little oscillation as possible withregard to possible oscillations in a direction of the optical axis 200.This is necessary since any oscillation excitation which has anoscillation component 202 in a direction of the optical axis 200 and anamplitude within the range of 1 to 10 μm makes it impossible to positionthe optical component 1 within the time mentioned. This is owing to thefact that the oscillations 202 usually decay very much more slowly thanthe time available for positioning the optical component 1 in its endposition B, the time being less than 500 ms (e.g., less than 50 ms, lessthan 5 ms). This relatively slow decay behavior of the constrainedoscillations is caused by the fact that the oscillation frequencies arein the range from a few Hz up to a few kHz.

The precision with regard to the actuating accuracy of the opticalcomponent 1 relative to its end position B of between 1 and 10 μm withina minimal time within the range of a new ms to 500 ms can advantageouslybe obtained within a lithographic projection exposure apparatus via thepresent disclosure, as has already been explained above in connectionwith FIGS. 1 and 2.

The disclosure therefore includes a lithographic projection exposureapparatus including an optical component that can be moved by a distancealong a straight line within a positioning time. In this case, theoptical component 1 includes one or a plurality of optical elements 34,which, if appropriate, also have mount elements. The straight linegenerally furthermore has a polar and azimuth angle of between 0° and90°. These angles define the direction of the straight line or of thedegree of freedom of movement along which the optical component 1 canmove. Furthermore, the distance between the straight line and an opticalaxis is less than a cross-sectional dimension of a projection exposurebeam bundle of the projection exposure apparatus. Since the straightline need not necessarily intersect an optical axis within theprojection exposure apparatus, since this is dependent on the opticalcomponents used, the straight line can also be spaced apart from theoptical axis. According to the disclosure, the optical component 1 isguided by a guide unit or guide device (e.g. a linear guide) having aguide direction and is driven via a drive or adjusting unit (actuatingunit) having a drive direction via drive forces in such a way that thetorques generated by inertial forces of the optical component 1 and ofpossible components concomitantly moved with the optical component 1,and the torques generated by the drive forces, which act on the guideunit, compensate for one another down to a magnitude of less than 10%. Acomplete compensation is striven for in this case. However, this dependson the requirements with regard to positioning time and distance to bemoved, and also on the technical configuration of the guide unit.

In order to ensure no oscillation excitation of the guide unit as far aspossible also at a constant speed of the optical component 1, the driveunit can be configured in such a way that the forces transmitted to theguide unit, in a direction perpendicular to the guide direction, areless than 10% of the drive force in a direction of the straight line orin a direction of movement. Here, too, a best possible avoidance of suchforces is striven for, wherein ideally no forces act perpendicular tothe guide direction.

In the case of lithographic projection exposure apparatuses, the movabledistance of the optical component 1 is between 20 mm and 1000 mm,wherein, as already mentioned, the positioning time is between 5 ms and500 ms.

As already becomes clear in the previous examples, the guide directioncan be arranged, apart from production and alignment tolerances,parallel to the straight line along which the optical component 1 ismoved. This requires a stiff and rigid linking of the optical component1 to the guide unit. Of technical interest are those movements of theoptical component 1 which enable a horizontal or vertical displacement.Displacements along an optical axis of the projection exposure apparatusor perpendicular thereto are likewise advantageous. Moreover, it can beadvantageous to permit the straight line to intersect the optical axisor to bring it to coincidence therewith.

If the optical component 1 includes for example a rotationallysymmetrical optical element, or an optical element 34 which has arotationally symmetrical effect on the projection exposure beam bundleat least in sections, then the optical component 1 can be opticallycentered with respect to the straight line along which it moves. In thiscase, optical centering is understood to mean that e.g. an opticalelement 34 having the symmetry properties mentioned lies with its pointof symmetry on the straight line.

FIG. 2c illustrates this, wherein the essential components are onlyillustrated schematically. In this case, an optical component 1, whichhas e.g. a reflective surface on a substrate, such as e.g. the concavemirror illustrated in FIG. 2c , is displaced along the optical axis 200in the X direction. In this case, the optical component 1 having thereflective surface can also be e.g. a diffractive optical element, suchas e.g. a reflection grating, but it can also be e.g. a mirror array. Inthis case, the optical element 1 is guided via the slide 462 and theguide 463, wherein the guide axis 460 of the linear guide 463 isoriented parallel to the optical axis 200 within the scope of theproduction and alignment tolerances. Furthermore, the guide 463 with itsslide 462 has no drive unit serving for the linear drive of the opticalcomponent 1. In this case, the guide 463 and the slide 462 can be, forexample, an air cushion guide, a magnetic guide, or in the form of asliding or rolling bearing guide. The optical component 1 is driven viaa drive unit 300, which likewise includes a slide 362 and a guide 363.The drive unit 300 can be designed analogously to the adjusting unitillustrated above. The drive unit 300 usually has a drive axis 360oriented parallel to the guide axis 460 of the guide 463 of the opticalelement. In this case, the drive unit 300 can be configured e.g. as anelectromagnetic linear drive, as has already been described above inconnection with the exemplary embodiments of FIGS. 1 to 2 b. In thiscase, the drive slide 362 acts on the optical element in such a waythat, via an operative connection 364, the drive forces (accelerating ordecelerating forces) pass with their force action line through orsubstantially through the centroid 103 of the optical component 1. Inthis case, analogously to the explanations concerning in FIGS. 2a and 2b, the centroid 103 is not necessarily arranged on the optical axis 200,as is illustrated merely by way of example in FIG. 2c . For the casewhere the drive unit 300 likewise represents a guide for the opticalcomponent 1, the latter would be mounted in a statically overdeterminedmanner, whereby forces and moments would be input onto the opticalelement. In order to avoid this, a moment decoupling element (notillustrated in FIG. 2c ) is advantageously fitted to the operativeconnection 364, which can include e.g. a ball-and-socket joint on whichthe drive force acts and from which the drive force is transmitted tothe optical component 1.

If the mass ratio between optical component 1 and the mass of the guideslide 462 is such that the mass of the slide 462 is no longer negligiblein comparison with the mass of the optical component 1, then theoperative connection 364 is chosen such that the force action line ofthe force applied by the drive unit 300 passes through the overallcentroid of optical component 1 and guide slide 462. In this case,possible mount element for the optical component 1, which connect theoptical component 1 to the guide slide 462 and hold it in position, arelikewise taken into account. Such a directing of the drive force ontothe system including optical component 1 and guide slide 462 has theadvantage that the drive force and the inertial force caused by themasses of the guide slide 462 and of the optical component 1 uponacceleration (or deceleration) add up to zero, for which reason notorque having a component perpendicular to the optical axis 200 orperpendicular to the guide axis 460 is transmitted to the guide 463 viathe guide slide 462. An oscillation excitation of the guide 463 duringthe movement of the optical component 1 along the optical axis 200 thusfails to occur, thereby enabling the optical component 1 to be rapidlypositioned into an end position with extremely high precision.

At very high speeds or accelerations of the optical component 1, a nolonger negligible friction force occurs at the guide 463 and at theslide 462, depending on the technical configuration of the guide, whichfriction force, in the embodiment according to FIG. 2c , can likewiseexcite the guide 463 to oscillation. This is because as a result of thefriction force, which occurs e.g. also at a constant speed of theoptical component 1, the drive unit 300 has to counteract this frictionforce via the operative connection 364 via a force that iscorrespondingly identical in magnitude but directed in the oppositedirection, in order to overcome the friction force F_(R). This force Fapplied by the drive unit 300 and introduced via the operativeconnection 364 brings about a torque M_(R) in a direction perpendicularto the guide axis 460, as is illustrated schematically in FIG. 2d . Inthis case, FIG. 2d shows an excerpt from FIG. 2c with the presence offriction forces between guide 463 and slide 462 during constant movementof the optical component 1 along the axis 200, that is to say in arrowdirection x. Since the friction also occurs during acceleration, thefriction force additionally has to be overcome there as well. This makesit necessary for the drive force that acts on the optical element fromthe drive unit 300 via the operative connection 364 not only to bepredetermined by the necessary acceleration but to be increased by themagnitude of the friction force F_(R) with regard to its magnitude. Thisincreased magnitude of the drive force is not compensated for by theinertial force F_(T) with regard to the generation of torques. Thisnon-compensated force likewise generates, as illustrated above, a torqueperpendicular to the guide axis 460 or perpendicular to the direction ofmovement, which takes place along the optical axis 200 in the exemplaryembodiment shown. This torque can excite the guide 463 of the opticalcomponent 1 and hence the slide 462 and the optical component 1 toeffect oscillations, thereby preventing a rapid precise positioning.

In the case where virtually speed-independent sliding friction ispresent, the influence of the friction forces F_(R) and the influence ofthe torques M_(R) associated therewith can be reduced firstly bytemporally minimizing the uniform movement of the optical component 1during the adjustment of the optical component 1 or by completelydispensing with a uniform movement. Secondly, the acceleration can bechosen in such a way that an inertial force F_(T) acts which is equal tothe drive force F reduced by the magnitude of the friction force F_(R).In addition, the operative connection 364, at which the drive force isintroduced onto the optical component 1, between the optical component 1and the slide 462 is no longer introduced in such a way that the forceaction line passes through the common centroid thereof, as was mentionedin connection with FIG. 2c . The operative connection 364 is chosen insuch a way that the inertial force acting at the common centroid 103(which results from optical component 1 and the slide 462) and thetorque M_(T) associated therewith precisely compensate for the torqueM_(F) generated by the drive force. Since the inertial force F_(T) isgiven and the drive force F is increased by the friction force F_(R), itis the case that F_(T)=F−F_(R) holds true, where F_(T) is <F, an offsetV of the centroid 103 in a direction of the guide axis 460 is necessaryfor the operative connection 364 in order to obtain the abovecompensation of the torques M_(T)=M_(F). The drive force F is thenintroduced into the operative connection 364, displaced by the offset V,in such a way that the force action line, instead of passing through thecentroid, is displaced by the offset V parallel thereto in a directionof the guide axis 460. This force situation is illustrated schematicallyin FIG. 2e , which shows the forces occurring in FIG. 2d in relation tothe common centroid 103 together with the offset V. In the case of theguides 462, 463 used in projection exposure apparatuses in the course ofprecise positioning, the friction force is usually very much smallerthan 0.001 times the drive force. In the case of aerostatic or magneticguides, the friction force tends toward zero, such that the offset isvery small and often negligible.

On account of the above explanation, the present disclosure encompassesembodiments in which an optical component 1 is guided linearly asprecisely as possible via a guide device, and to move the opticalcomponent 1 linearly along the device. In this case, via a drive unit300 or an actuating unit 2, a drive force F is directed into the opticalcomponent 1 in such a way that neither forces nor torques havingdirection components perpendicular to the direction of movement of theoptical component 1 input onto the guide 463 by the drive force F. Inthis case, the direction of movement of the optical component 1corresponds to the guide axis 460 of the guide 463 apart from productionand alignment tolerances. Via this, according to the disclosure, anoscillation excitation of the guide 463 of the optical component 1 (andhence also of the optical element 1) by the drive force F of the driveunit 300 is prevented or at least reduced to an extent such that highlyprecise linear position changes of the optical component 1 within a veryshort time in the range of ms, such as, for example, between 5 msthrough to 500 ms, are made possible.

In order also to displace or position transparent optical component 1according to the embodiments described in FIGS. 2c to 2e , thedrive-force-transmitting operative connection 364 a of the opticalcomponent 1 is configured in such a way that e.g. the optical component1 is connected to the drive unit in each case at an edge region in sucha way that a straight line through the edge regions intersects thecentroid 103, wherein the straight line can be chosen to beperpendicular to the plane spanned by the optical axis 200 and the guideaxis 460. This is illustrated in the exemplary embodiment according toFIG. 2f . This schematically shows a section perpendicular to thedirection of movement, which is intended to be identical to the opticalaxis 200, wherein the optical component 1 (or the optical component) isprovided with edge regions 110, 111 at which the drive forces generatedby the drive slide 362 of the drive unit 300 with the drive axis 360 isinput via a suitable operative connection 364 in the direction ofmovement. In this case, as mentioned above, the operative connection caninclude elements which permit a moment decoupling, as is the case e.g.for ball-and-socket joints. The abovementioned straight line isdesignated by 112 and runs through the common centroid 103 of theoptical component 1 and of the slide 462 perpendicular to the spannedplane. In the case of friction in accordance with the embodimentsaccording to FIG. 2d , the straight line has a corresponding offset Vaccording to FIG. 2e and runs in a manner displaced parallel by theoffset parallel to the straight line 112 shown in FIG. 2f in a directionof the guide axis 460. In order to avoid a statically overdeterminedguide of the optical component 1, a dedicated drive device that actswith its respective drive force on the edge regions 110 and 111 can ineach case be provided instead of the drive device 300 with the driveaxis 360 (also see FIG. 2c ). The drive devices that act on the opticalcomponent 1 in such a way are controlled or regulated independently ofone another. This embodiment corresponds to the embodiment of thedisclosure illustrated in FIG. 1, wherein the drive units have paralleldrive directions apart from production and alignment tolerances.

In the context of the knowledge according to the disclosure that inlithography apparatuses a precise and rapid positioning of opticalcomponent 1 in accordance with the above explanations necessitates asfar as possible avoiding (or minimizing) oscillation excitations of theguides of the optical component 1 by the forces of the drive system,FIG. 2g shows a further embodiment, based on the embodiment of FIGS. 2aand 2b . Guide axis and drive axis coincide here as in the exemplaryembodiment according to FIGS. 2a and 2b . In this case, the opticalcomponent 1 connected to the slide 62 is guided via the slide in such away that on account of the length SL of the slide in a direction of theguide axis 60, the oscillation amplitude 202 of the optical component 1in the direction is reduced, wherein the oscillations essentially resulton account of the mechanical play between the guide slide 62 and theguide 63. In this case, the guide slide can be dimensioned in such a waythat the oscillation amplitudes that are possible as a result of thebearing play in the region and in the direction of the optical axis 200is less than L=10 μm. Given a typical bearing play of y=1 μm, this meansthat for instance y/SL=L/b. In this case, SL is the length of slide 62and b is the distance between the guide axis 60 and the optical axis200. By way of example, if b exhibits 50 mm, this results in a length ofthe slide 62 of SL=5 mm. This means that for the bearing play of 1 μmand the distance b of approximately 50 mm, the slide 62 should have atleast a length of 5 mm in order, on account of the mechanical play, tobe able to position the optical component 1 within the desiredpositioning accuracy of better than 10 μm in the region of the opticalaxis. More generally, the above condition can be formulated in such away that the guide unit includes a slide guided by a guide and havingguide areas spaced apart by a magnitude SL in a guide direction. In thiscase, the guide and the guide slide have a bearing play y. Furthermore,between an oscillation amplitude L—occurring in a direction of thestraight line (along which the optical component 1 moves)—of the opticalcomponent 1, which is spaced apart from the guide by the magnitude b,the relationship SL>y*b/L is intended to be complied with. In practice,SL values in the range of 3 to 10 times the distance between thecentroid of the optical component 1 and the guide often result in thiscase, wherein, if the structural space is available, even the 10-foldvalue can be exceeded, as is explained in more detail below.

The abovementioned condition with regard to the bearing play can besupplemented further by also reducing a reduction of the effect of thetorque effects that arise as a result of the inertial force F_(T), andits effects with regard to constrained oscillations. During decelerationof the optical component 1, the inertial force F_(T) generates a torqueM_(T), which is compensated for by a torque generated by the forceF_(S), wherein the force F_(S) acts at least in the vicinity of a slideend. In this case, approximately F_(S)*SL=M_(T). These are onlyapproximations since, depending on the configuration of the slide 62 andthe guide 63, given the presence of bearing play, the possible axes ofrotation about which the slide 62 is induced to rotate on account of thetorques caused on account of the inertial forces are not preciselydefined. Furthermore, the exact torque condition also depends on theposition of the optical element 1 relative to the slide 62. Overall itcan be stated, however, that the oscillation excitation of the guide 63will turn out to be all the smaller, the smaller the force F_(S) actingon the guide. The force can be reduced by suitable configuration of thelength SL of the guide slide 62 to approximately 10% of the inertialforce F_(T) which results during acceleration or deceleration of theoptical component 1 (the optical component 1) together with the slide62. It is thus possible to specify a rough dimensioning rule that can berepresented on the basis of a torque equilibrium in the formF_(T)*b=F_(S)*SL=0.1×F_(T)*SL. This permits the determination of SL,wherein SL is then approximately 10*b. In this case, b, as illustratedin FIG. 2g , is the distance between the guide axis 60 and the opticalaxis 200. The first condition with regard to the bearing play isgenerally fulfilled via the dimensioning rule. What is disadvantageousabout this dimensioning is that in general the slide 62 exceeds thelength of 10 cm up to 50 cm, whereby an increased mass isdisadvantageously to be moved, which results in an increased drivepower. Furthermore, the necessary structural space for this demonstratedinventive solution according to FIG. 2g is often not available.

In a further embodiment of the disclosure, the embodiment according toFIGS. 2a, 2b is modified in such a way that a balancing mass M_(A) isfitted on a side opposite to the optical component 1 with respect to theguide axis 60, as is indicated schematically in FIG. 2g . The balancingmass M_(A) is rigidly connected to the slide 62 and chosen with regardto size and distance from the guide axis 60 in such a way that theinertial force proceeding from it during acceleration of the opticalcomponent 1 generates a torque in such a way that the torque M_(T) ofthe optical component 1 (and possibly of the slide) is preciselycompensated for. This means that no resultant torque arises in adirection perpendicular to the guide axis 60 during acceleration ordeceleration of the optical component 1. By virtue of this measure,during acceleration of the optical component 1, the guide axis 60 islikewise not excited to effect oscillations, or is at least only excitedto effect oscillations to a reduced extent. What is disadvantageoushere, too, is that an additional mass has to be moved, which increasesthe drive power and which requires an additional structural space.

FIGS. 3a, 3b and 3c show various possibilities for varying thearrangement of optical component 1, actuating units 2 and linear guide6. In the variant illustrated in FIG. 3A, the two optical components 1are in each case guided on dedicated linear guides 6 in a direction ofthe optical axis, wherein the actuating units 2 serve for the drive, theactuating units being in the form of Lorentz linear actuators in theexample shown. In the example shown, the permanent magnet 4 ismechanically connected to the optical component 1 and concomitantlymoves with the latter; it goes without saying that a variant in whichthe coil 5 is mechanically connected to the optical component 1 is alsoconceivable. In this case, the linear guide 6 can be, for example, arolling bearing guide, sliding bearing guide, air or magnetic bearingguide.

FIG. 3B shows a variant which is modified by comparison with thearrangement in FIG. 3A and in which the arrangement of the opticalcomponents 1 on the linear guides 6 is realized oppositely to theembodiment shown in FIG. 3A, whereby the required structural space canbe reduced in the direction orthogonal to the optical axis.

FIG. 3C illustrates a variant in which the two optical components 1 areguided on a common linear guide 6, which likewise results in a reductionof the required structural space. In this case, a magnetic arrangementis used jointly by a plurality of optical components, but each forceaction point on each optical component 1 can be regulated or controlledcompletely independently of the other force action points.

In the exemplary embodiments illustrated in FIG. 3, two opticalcomponents 1 are moved by the same Lorentz linear actuator as actuatingunit 2. A further advantage of the use of a Lorentz linear actuator asactuating unit 2 becomes clear as a result of this: on account of thepurely electronic driving, it is possible for two optical components 1to be moved independently of one another by the same actuator merely viaa suitable driving.

FIG. 4 shows, in a section orthogonal to the optical axis, a variant ofthe disclosure in which the linear guides 6 are realized as airbearings. In this case, the four air bearings 6 are arranged oppositeone another respectively in pairs between the two actuating units2—realized as Lorentz linear actuator—along the inner circumference ofthe housing 7. The use of air bearings as linear guides 6 has theadvantage that a mechanical sliding contact is obviated and a frictionof mechanical components against one another is thus precluded. Thiseffectively avoids firstly the desire for lubrication and also the riskof particle abrasion of the mechanical components rubbing against oneanother. The use of air bearings is thus advantageous particularly inthe case of high cycle numbers. As an alternative to the air bearings,it is also possible to use rolling bearings for the linear guide; suchball recirculation or else cross roller guides have the advantage thatthey can be designed as components having a high stiffness.

FIGS. 5a and 5b show two embodiments of the device according to thedisclosure in which the weight force of the optical component 1 iscompensated for. In FIG. 5a this is achieved via the counterweight 9,which acts on the optical component 1 in the region of the linear guide6 via a cable pull 11 via the deflection rollers 10. FIG. 5b shows thevariant wherein the weight force is compensated for by the two pneumaticcylinders 17 a and 17 b with gap seals. In this case, the two pneumaticcylinders 17 a and 17 b are arranged on the optical component 1 in sucha way that the straight line through the points of action of the twopneumatic cylinders 17 a and 17 b runs through the centroid of theoptical component 1 and, as a result, no additional moments arise at theoptical component 1. This variant has the effect that the total mass tobe moved during the positioning of the optical component 1 is keptsmall. The compensation of the weight force of the optical component 1has the advantage that the actuating units can merely be used to bringthe optical component 1 to the desired position as necessary, ratherthan having to hold the position of the optical component 1 against itsentire weight force during operation. The use of the weight forcecompensation illustrated is appropriate particularly for cases where theoptical axis of the optical system and thus the movement axis of thedevices lie in a vertical direction. In other words, the actuating unitcan be used exclusively for moving the optical component 1 and not forworking on it against the gravitational force, which would lead to aconsiderable heating of the actuating unit 2. If the optical axis and/orthe direction of movement of the optical component 1 has a directiondeviating from the horizontal, then the weight force resolved byresolution of forces in a direction of the direction of movement and ina perpendicular direction thereto is compensated for in a direction ofthe direction of movement. This compensation can be effected inaccordance with FIGS. 5a and 5b . This affords the advantage that onlythe inertial forces and friction forces have to be applied for movingthe optical element.

FIG. 6 shows a further embodiment of the device according to thedisclosure, in which the optical components 1, in addition to adisplacement in a direction of the optical axis of the optical system,can also be pivoted out of the region of the optical axis or into theregion of the optical axis. For this purpose, the actuating unit 2 a isprovided with the two axial actuating mechanism 13 a and with thepivoting mechanism 14 a, by which the abovementioned movements of theoptical components 1 a can be carried out. The optical system isadditionally provided with the actuating mechanism 2 b, which, for theirpart, have the axial actuating mechanism 13 b and the pivoting mechanism14 b; in FIG. 6, the optical components 1 b connected to the secondactuating unit 2 b have been pivoted out of the beam path of the opticalsystem and thus out of the optical axis indicated by a dash-dotted line.The embodiment illustrated in FIG. 6 permits the optical properties ofthe optical system and hence the operational configuration of theoptical system to be changed over in an extremely rapid manner. For thispurpose, it is merely necessary for the optical components 1 a situatedin the beam path to be pivoted out of the beam path by the pivotingmechanism 14 a and, simultaneously or shortly afterward, for the opticalcomponents 1 b to be pivoted into the beam path of the optical systemusing the pivoting mechanism 14 b. In this case, the optical components1 b can already be brought into their axial position along the opticalaxis by the axial actuating mechanism 13 b before the pivoting-inprocess, that is to say still during the operation of the optical systemin the first operational configuration, such that this step does notlead to a loss of time when changing over the optical system from oneoperational configuration to the next. In the example shown, the opticalcomponents 1 a are merely replaced by the optical components 1 b, whichare substantially identical to them with regard to their opticalproperties, at other locations along the optical axis in the opticalsystem. However, the case where the optical components 1 that can bepositioned by the actuating units 2 a and 2 b have different opticalproperties is also conceivable. In this case, further optical degrees offreedom result for the possible operational configurations of theoptical system.

FIG. 7 shows an embodiment of a pivoting mechanism 14, corresponding tothe pivoting mechanism 14 a, 14 b from FIG. 6, for pivoting the opticalcomponent 1 into or out of the beam path of the optical system, in whicha prestress element 18 and a releasable retention element 19 areprovided. In this case, the prestress element 18 is an electromagnetwhich, upon its activation, has an attracting effect on the magnetizablepart of the optical component 1 that faces it. In this case, therotation of the optical component 1 about the axis indicated by thearrow in the shape of an arc of a circle in FIG. 7 is initiallyprevented by the releasable retention element 19. At the instant atwhich the releasable retention element 19 is moved in a direction of thearrow, the optical element 1 is rotated on account of the magneticattraction force between the electromagnet and the magnetizable part ofthe optical element 1. A rapid pivoting of the optical component 1 canbe ensured in this way. If appropriate, an electromagnet (notillustrated) can likewise be present on the opposite side to theprestress element 18, via which electromagnet the movement of theoptical component 1 into its original position can be achieved; arestoring of the of the optical component 1 via a resilient element(likewise not illustrated) is equally conceivable.

FIG. 8 shows a further exemplary embodiment of the disclosure, whichtakes account of the requirement that, particularly during a rapidpivoting of the optical component 1, as illustrated in FIG. 7, forexample, without corresponding countermeasures, parasitic forces/momentssuch as e.g. transverse forces or tilting moments act on the bearingabout which the optical component 1 is pivoted.

Such parasitic forces and/or moments can be effectively minimized, asillustrated in FIG. 8, by the balancing mass 20 being arranged on theopposite side of the optical component 1 with respect to the bearingpoint 21. In this case, the position of the centroids S′ of the opticalcomponent 1 and of the centroid S″ of the balancing mass 20 with respectto the bearing point 21 are chosen such that the following holds true:

$\frac{r}{R} = {\frac{M}{m}.}$wherer: distance between the centroid S′ of the optical component 1 and thebearing point 21R: distance between the centroid S″ of the balancing mass 20 and thebearing point 21M: mass of the balancing mass 20m: mass of the optical component 1.

In this case, the bearing point (21) should be understood as the pointat which the plane in which the pivoting/rotation of the centroid S′ ofthe optical component (1) is effected intersects the axis ofrotation/pivoting axis. If the above condition is complied with, thenthe bearing force in a radial direction of the rotation axis uponrotation is minimized in the sense that no centrifugal or centripetalforces occur whose vector sum is not equal to zero, since the axis ofrotation of the arrangement passes through the common centroid. Thisavoids excitation of any oscillations of the axis of rotation as aresult of a possible unbalance which, after reaching an end position ofthe optical component 1, have the effect that the latter performsoscillations about the end position, such that the position of theoptical component 1 varies relative to the optical axis or in adirection of the optical axis.

The moment of inertia I of the overall arrangement is calculated as asum of the two moments of inertia with respect to the bearing point 21asI=mr ² +MR ² +I _(m) +I _(M).

Substitution leads to

$I = {{{mr}^{2}( {1 + \frac{R}{r}} )} + I_{m} + {I_{M}.}}$

In this case, I_(m)+I_(M) are the moments of inertia of the opticalcomponent 1 with the mass m and, respectively of the balancing mass Mrelative to the respective axis of rotation which passes through therespective centroid of the optical component and of the balancing mass,and which run parallel to the abovementioned axis of rotation/pivotingaxis through the bearing point 21.

It becomes clear from the relationships illustrated that the variantillustrated in FIG. 8 opens up the possibility, given a suitable choiceof R, that is to say of the distance between the balancing mass 20 andthe location of the bearing 21, of providing the possibility that, viathe use of the balancing weight 20, the parasitic forces on the bearing31 are largely minimized without the total moment of inertia I of theentire arrangement of optical component 1 and balancing mass 20 assumingsuch a high value that a rapid pivoting of the arrangement about thebearing point 21 is made excessively more difficult. This is achieved bymaking the radius of the balancing mass M from the axis of rotation assmall as possible, which as a counterpart action means an increase inthe balancing mass M. The measure illustrated in FIG. 8 thus has theeffect that a subsequent oscillation of the overall arrangement afterthe rapid pivoting of the optical component 1 into the beam path of theoptical system is shortened considerably and the optical system reachesits operational readiness more rapidly after the pivoting. It goeswithout saying that the use of the balancing mass 20 for reducingparasitic forces in bearing points is not restricted to the variantillustrated in FIG. 8; it is likewise conceivable for the teaching ofFIG. 8 also to be applied to the arrangements illustrated in FIGS. 1 to5, for example as a supporting measure.

FIG. 9 shows an optical system in which the principles described abovecan advantageously be employed.

The system described with reference to FIG. 9 is a subsystem 30 of anillumination system of a projection exposure apparatus for semiconductorlithography as far as the first pupil plane 31, which is indicated viathe dashed line in FIG. 9. The light distribution—usually referred to assetting—in the pupil plane 31 is set by way of the beam deflection of apreviously homogenized and collimated laser beam 33 via a micromirrorarray (MMA) 32 in a field plane. The other optical elements illustratedin FIG. 9, which are designated in combination by the reference symbol34, serve for beam shaping on the path of the laser beam 33 from themicromirror array 32 as far as the pupil plane 31; they are notdiscussed explicitly below.

The method of so-called double exposure, which is widespread insemiconductor lithography, imposes on the illumination system therequirement of changing between two settings within a few milliseconds,such as within the range of 10 to 30 milliseconds. In this case, thefrequency of the changes themselves is of a similar order of magnitude.This setting change means that thousands of the micromirrors (notexplicitly illustrated in FIG. 9) arranged on the micromirror array 32have to be adjusted per change of the setting. The associated mechanicalloading on the micromirrors leads, particularly in the case of a highnumber of cycles, to the occurrence increasingly of mechanical failuresof individual mirrors or a shortening of the recalibration intervals forthe absolute mirror position on account of drift. The objective consistsin minimizing the mechanical loading on the individual micromirrors ofthe micromirror array 32 during the fast setting changes described.

This can be achieved in accordance with the exemplary embodimentillustrated in FIG. 9 by dividing the micromirror array 32 into at leasttwo partial regions. In this case, each partial region of the tworegions mentioned contains approximately half of all the micromirrorsor, given a subdivision into three partial regions, for example, a thirdof all the micromirrors, etc. The first partial region is configured,with regard to the position of the individual micromirrors, to the firstsetting to be chosen, whereas the second partial region, with regard tothe arrangement of its micromirrors, is adapted for the second setting.For a change of the setting, in accordance with the exemplary embodimentshown in FIG. 9, the individual micromirrors of the entire micromirrorarray 32 are now no longer adjusted, rather care is merely taken toensure that exclusively that partial region of the micromirror array 32which is respectively adapted to the chosen setting is illuminated. Thishas the effect that, in the event of a change of the setting, themicromirrors themselves do not have to be moved since only a differentillumination of the micromirror array 32 is chosen.

FIG. 10 illustrates, in the upper region of the figure, the two lightdistributions that are set alternately in the pupil plane 31. Setting 1(left-hand part of FIG. 9a ) in this case shows the locations—calledpoles—having a high light intensity 210, 212, 213 and 214, whereassetting 2 (right-hand part of FIG. 9a ) shows the poles 215, 216, 217and 218.

In the example illustrated in FIG. 10, setting 1 is produced by the beamdeflection of the micromirrors lying in the region 101 and 102 of themicromirror array 32, whereas setting 2 is produced by the illuminationof the micromirrors of the regions 103 and 104 (cf. lower part of FIG.9a ).

FIGS. 11a and 11b show the arrangement according to the disclosure forsetting the light distributions on the micromirror array 32. The opticalcomponents 1′ and 1″ are diffractive optical components in the variantillustrated in subfigures a and b in FIG. 11. It goes without sayingthat it is likewise possible to use refractive optical componentsinstead of diffractive optical components 1′ and 1″; one advantage ofthis variant is for example because refractive optical components aregenerally more efficient and cause less scattered light.

By displacing the optical components 1′ and 1″ in the beam path of thelaser beam 33 in a direction of the double-headed arrow 36 in such a waythat the optical component 1′ or 1″ is alternately situated in the beampath of the laser beam 33, what can then be achieved is that the regions101, 102 (optical component 1′) or 103 and 104 (optical component 1″) onthe micromirror array 32 are alternately illuminated. The lens 35 in thelight path between the optical components 1′ and 1″ and the micromirrorarray 32 serves for beam shaping in this case.

An essential aspect of the embodiment shown in FIG. 11 is that themicromirror array 32 is arranged in the pupil plane (not designated inFIG. 11) of the lens 35 and the light distribution on the micromirrorarray 32 is determined by the position or setting of the opticalcomponents 1′ and 1″ in the field plane upstream of the lens 35. In theexample illustrated in FIG. 11, the optical components 1′ and 1″ andalso the micromirror array 32 are arranged in a respective focal planeof the lens 35. In this case, it is advantageous if the focal length ofthe lens 35 has a highest possible value; ranges from 500 millimeters to100 millimeters can be advantageous here. The described arrangement oflens 35, optical components 1′ and 1″ and micromirror array 32 has theeffect that an approximately collimated illumination on the micromirrorarray 32 becomes possible, the illumination thus exhibiting littledivergence. In this case, the application of the possibilities shown inFIGS. 1 to 8 for rapidly changing the optical component 1 in the beampath of the optical system enable the rapid setting changes striven for;it goes without saying that it is likewise conceivable to apply theteaching of FIGS. 9 and 10 without resorting to the technical solutionsillustrated in FIGS. 1 to 8. Assuming that the laser beam 33 exhibits adiameter of approximately 20 millimeters and a switching time of 20milliseconds is necessary, the speed at which the optical component 1′or 1″ has to be moved in the beam path of the laser beam 33 isapproximately one meter per second, which represents a value that canperfectly well be controlled in respect of mechanical aspects.

One advantage of the embodiment illustrated in FIGS. 10 and 11 is thatthe shape of the pupil in the illumination system, in contrast to aprocedure according to the prior art, is not set via a for examplediffractive optical component without a micromirror array 32, but rathervia the micromirror array 32 itself. This has the effect that in theextreme case the number of optical components to be kept available canbe limited to two, since the micromirror array 32 exhibits the necessaryflexibility with regard to the settings to be set. It goes withoutsaying that the arrangement and the geometry of the regions 101 to 104is not restricted to the form illustrated in FIGS. 9 and 10. In asimplified embodiment, a mirror can be used as the optical component 1,which mirror is shifted to and fro or else tilted in the beam path ofthe laser beam 33 in order to illuminate the different regions, such as101 and 102 for example, on the micromirror array 32. This embodiment isdepicted schematically in FIG. 12. It goes without saying that the useof prisms, beam deflectors or other optical components is alsoconceivable.

A subdivision of the regions 101, 102 and/or 103, 104 into subregionshaving a different polarization enables a change in polarization at thespeed discussed above. For this purpose, the polarization in each of theregions mentioned is set by 90° rotators, that is to say opticallyactive plane plates, in the arrangement of a so-called “Schuster plate”.The “Schuster plate” includes at least two birifrigent elements having adifferent orientation of the crystal axes or thicknesses with respect toone another. It utilizes the linear birefringence in order to convert afirst polarization distribution into a second polarization distributionvarying locally in its profile. A detailed description of thefunctioning is contained in DE 195 35 392 A1. FIG. 13 shows a possibleassignment between the polarization, the partial regions 101, 102, 103,104 of the micromirror array 32 and the poles of the settings 210, 212,213, 214, 215, 216, 217, 218 in the pupil plane 31 (cf. FIG. 13). Thelight linearly polarized in the y direction becomes linearly polarizedlight in the x direction in the region 101 owing to the use of a 90°rotator (not illustrated) that covers the region 101.

Further rotators in the regions 103 and 104 correspondingly rotate by45° and −45°, respectively, relative to the orientation of the laserpolarization. In this case, in a known manner, the polarization rotationis proportional to the thickness of the optically active substrate ofthe rotator, whereby different angles of rotation can be realized.

FIG. 14 shows a further variant, which is suitable for generatingrotationally symmetrical light distributions on the micromirror array32. In this case, the micromirror array 32 is divided into the tworegions 101 and 102 having a different functionality. In the exampleshown in FIG. 13, the optical component 1 is realized as one of the twoconical lenses of an axicon 40. The two conical lenses hollow cone inone instance and as cone in one instance and have an identical acuteangle. Furthermore, the distance B between the two conical lenses isadjustable. For the case where the two conical lenses are in contactwith one another, and the distance B is equal to zero, this results in alight distribution in the form of a circle. Where B is greater thanzero, the beam 33 is expanded to the effect that this results in anannular light distribution with a dark field in the center. Afterpassing through the axicon 40, the laser beam 33 impinges on the lensarrangement including the lenses 37, 38 and having a variable distanceD, which lens arrangement acts in the manner of a zoom lens and expandsthe laser beam 33. The neutral filter 39 is arranged in the furthercourse of the light path in a direction of the micromirror array 32. Asetting of the distance B between the two conical lenses of the axicon40 in conjunction with the setting of the distance D between the twolenses 37 and 38 makes it possible to illuminate, alternatively or elsejointly, the partial regions 102 and/or 101 on the micromirror array 32.In addition, an arrangement for beam homogenization can be disposed (notillustrated in FIG. 13) in the light path upstream of the axicon 40.

The beam conditioning can be implemented in such a way that any desiredlight distributions on the micromirror array 32, such as, for example,multipoles, segments or the like, are possible. For this purpose, it ispossible, if appropriate, to adapt the geometry of the conical lenses ofthe axicon 40; a prismatic embodiment of the conical lenses isconceivable, by way of example.

An abaxial illumination of the micromirror array 32 is also possible.For this purpose, the relative orientation between the laser beam 33 andthe axicon 40 is changed; by way of example, the position of the laserbeam 33 on the axicon 40 is displaced in the z-y plane. This can beeffected for example by two tiltable mirrors (not illustrated) disposedupstream of the arrangement. This makes it possible to illuminate onlythe upper partial region of the micromirror array 32 by a displacementof the laser beam 33 upward (z direction).

For intensity correction in the pupil plane 31 already on the plane ofthe micromirror array 32, it is possible for example to use the neutralfilter 39 illustrated in FIG. 15. In the neutral filter 39 shown in FIG.15, the light is attenuated to a greater extent in the central region231 than in the peripheral region 232. In this case, the region 231corresponds to the region 101 on the micromirror array 32, the region232 corresponding to the partial region 102 on the micromirror array 32.The embodiment of the neutral filter 39 depends on the magnitude of theparameters D and B. Consequently, it will be necessary to introducedifferent neutral filters 39 into the beam path depending on the settingchosen. In this case, for rapidly changing the neutral filters, it ispossible to have recourse to the concepts illustrated with reference toFIGS. 1 to 8.

Correspondingly, the teaching illustrated in FIGS. 1-8 can be employedfor the manipulation of the optical components 1, 1′, 1″ illustrated inFIGS. 11, 12 and 14; a realization independently thereof is likewisepossible, of course.

A further possibility for setting the desired settings, which managescompletely without linearly accelerated masses in the system and theinertia effects associated therewith, is described below with referenceto FIG. 16: the optical component 1 is accordingly realized as arotating, for example circular, disk with partial elements 1′ 1″ ascircle sectors. In principle, it suffices to embody the opticalcomponent 1 in such a way that it has at least two optical partialelements which can each be introduced periodically at a specificfrequency f into a beam bundle used for illumination, such as into thelaser beam 33, for example. In the case of the rotating circular disk,the rotational angular frequency 2πf of the optical component 1corresponds here for example to the pulse frequency of a laser used forillumination. This has the effect that the light used for illuminationis always incident on the same optical partial element 1′ or 1″ of therotating optical component 1. When using a CW (continuous wave) laser,the necessary pulses can be generated for example by the use of aperiodically operated shutter or a chopper wheel.

The choice of the partial element 1′ or 1″ to be used and thus of thedesired setting is effected in this case via the start instant of thesequence of laser pulses used for the respective exposure, of theso-called burst. The essential advantage of this variant is thatchanging the setting does not require any accelerated linear orrotational movements of to optical elements in the light path and thusin the system. This means that no oscillations on account of theinertial forces are input into the system. The setting is chosen purelyelectronically via the synchronized, temporally controlled choice of thestart instant of the respective burst. In order to obtain a temporallystable radiation distribution, it is advantageous if the radiationdistribution generated by the partial elements 1′ and 1″ does not changewhile the respective partial element 1′ or 1″ stays in the beam bundle33, which can be achieved via a corresponding geometrical configurationof the partial element 1′ or 1″. In order to minimize undesirableeffects when the respective partial element 1′ or 1″ enters into orexits from the beam bundle 33, the length and the start and end instantsof the pulses can be chosen in such a way that the entrance and the exitof the respective partial element 1′ and 1″ is effected during the darkphases between the pulses; in other words, in this case the pulsed beambundle 33 only ever lies completely on one of the partial elements 1′ or1″.

What is claimed is:
 1. An illumination system, comprising: an opticalcomponent configured to set a radiation distribution in a pupil plane ofthe illumination system, the optical component comprising first andsecond partial elements configured to be periodically introduced into abeam bundle of the illumination system at a frequency f, wherein: thebeam bundle is generated using pulsed electromagnetic radiation, and apulse frequency of the electromagnetic radiation is the frequency f; theillumination system further comprises an optical element; the opticalcomponent is upstream of the optical element in a light path of theillumination system; and during use of the illumination system,different regions of the optical element are illuminated by periodicallyintroducing the first and second partial elements into the beam bundleof the illumination system at the frequency f.
 2. The illuminationsystem of claim 1, wherein the optical element comprises a micromirrorarray.
 3. The illumination system of claim 1, wherein the opticalcomponent comprises a diffractive optical element.
 4. The illuminationsystem of claim 1, wherein the optical component comprises a refractiveoptical component.
 5. The illumination system of claim 1, furthercomprising optically active elements upstream of the optical elementalong the light path, wherein the optically active elements areconfigured to set different polarizations for the different regions ofthe optical element.
 6. The illumination system of claim 1, furthercomprising an actuating unit configured to position the opticalcomponent.
 7. The illumination system of claim 6, wherein the actuatingunit comprises a Lorentz linear actuator.
 8. The illumination system ofclaim 6, further comprising a linear guide configured to guide movementof the optical component.
 9. The illumination system of claim 6, furthercomprising a displacement measuring system configured to determine theposition of the optical component, wherein the displacement measuringsystem comprises an encoder having a measuring head and a referencegrating.
 10. The illumination system of claim 6, further comprising acompensation device configured to compensate a weight force on theoptical component.
 11. An apparatus, comprising: an illumination systemcomprising an optical component configured to set a radiationdistribution in a pupil plane of the illumination system, the opticalcomponent comprising first and second partial elements configured to beperiodically introduced into a beam bundle of the illumination system ata frequency f; and a projection objective, wherein: the apparatus is aprojection exposure apparatus; the beam bundle is generated using pulsedelectromagnetic radiation, and a pulse frequency of the electromagneticradiation is the frequency f; the illumination system further comprisesan optical element; the optical component is upstream of the opticalelement in a light path of the illumination system; and during use ofthe illumination system, different regions of the optical element areilluminated by periodically introducing the first and second partialelements into the beam bundle of the illumination system at thefrequency f.
 12. The apparatus of claim 11, wherein the optical elementcomprises a micromirror array.
 13. The apparatus of claim 11, whereinthe optical component comprises a diffractive optical element.
 14. Theapparatus of claim 11, wherein the optical component comprises arefractive optical component.
 15. The apparatus of claim 11, wherein theillumination system further comprises optically active elements upstreamof the optical element along the light path, and the optically activeelements are configured to set different polarizations for the differentregions of the optical element.
 16. The apparatus of claim 11, whereinthe illumination system further comprises an actuating unit configuredto position the optical component.